The invention relates to the technical sector of automatic machines, step-operating or continuous, for packaging products such as pills, tablets and the like in blisters of a heat-formed strip, in order to obtain packs known as blister-packs.
In the above machines, known as blister packers, in a constructional design which is common to many realizations, a first operating line is included in which the smooth strip is unwound from a reel and taken to a forming station in which the blisters are made by heat-impression; the heat-formed strip then proceeds towards a filling station in which products are selected, ordered and supplied to inserting organs, which fill each blister, with usually a single product being placed in a single blister.
Downstream of the filling station are situated further stations in which the heat-formed strip, with the blisters filled, is sealed, controlled, cut to separate one blister pack from another; the properly-formed blisters packs are then supplied to an outlet station, while the defective ones are deviated to a reject station.
In the blister packer, the filling station is of particular importance, and so is the technical solution used for realizing the inserting organs.
The prior art comprises various forms of realization for the insertion organs.
A known solution comprises arranging, immediately above the blister strip, a sort of open-bottomed tray in which the products are supplied loose and plentifully and are caused to enter into the transiting underlying blisters, by force of gravity and with the aid of means for ensuring entrance of a single product per blister, its correct arrangement internally of the blister and a preferred distribution of the articles in the tray, in greater quantities upstream and smaller quantities downstream.
This solution has the advantage of not including specially-shaped organs either in relation to the product or to the arrangement or orientation of the blisters in the blister pack, so that upon changing the shape and arrangement of the blisters no component substitution is required.
The insertion of the products in the blisters has shown itself to be better when the products are disc-shaped than when they are elongate; in the latter case the difficulties in insertion increase if the blisters are transversally arranged with respect to the advancement direction of the heat-formed ribbon; further, the required increased re-sorting of the products in the tray has shown itself to be disadvantageous with regard to the integrity of some types of pills, i.e. those more fragile than the others.
A further known solution describes how to order the products in a direction towards a series of chutes, arranged aligned with the corresponding rows of cells transiting below and opening just above the upper surface of the heat-formed strip.
A row of products forms in each channel of the chute, which row is retained at the bottom by the heat-formed strip, in the zones between one blister and another, while the release of a product, by force of gravity, is allowed upon the passage of each of the concavities defining the blisters.
In variants of the above solution, intercepting organs are included at the base of the rows of products in the chutes, which organs are opened in phase relation with the passage of the blisters.
This solution requires a complex system of vibrating planes for supplying the chutes, made in a suitable shape, which therefore have to be replaced at each change of product format.
The conformation of the chutes, specific for each product format, does not prevent occasional clogging with a consequent halting of the descent of the pills; which clogging is more or less frequent according to the shape of the products themselves; further, the solution exhibits greater functionality, with elongate products, if the blisters are arranged parallel to the advancement direction of the heat-formed strip.
Another solution teaches the use of a master strip in which blisters are realized having the same shape and arrangement as the heat-formed strip.
The master strip develops in a closed-ring trajectory in which an upper branch and a lower branch are defined, with the lower branch facing and above the heat-formed strip, in phase relation there-with, such that the blisters are mutually aligned in the zone of common trajectory.
The products are inserted in the blisters of the master strip on the upper branch; the blisters are holed at the base and are placed in communication with a source of depression which places them in depression, such as to retain the products inserted both in the curved connecting tract and in a part of the lower branch, up to a predetermined point in which the aspiration is stopped, allowing the product to fall into the corresponding underlying blisters of the heat-formed ribbon.
In a further solution (see WO2005/075293) the master strip is provided with shaped blisters which are located at the side of the blistered ribbon, perpendicularly thereto.
The products are inserted in the blisters of the master strip at the zone thereof which is further from the heat-formed ribbon, and when the products reach the closest zone they are aspiratingly removed by means of a head having multiple gripping organs, borne by a robotic arm able to transfer the head onto the heat-formed ribbon in order to enable depositing of the products in the blisters thereof.
If the heat-formed ribbon is continuously activated, the robotic arm is able to move the head in order to follow the strip over a tract which is sufficient to enable discharge of the products.
The solutions with the master strip have the advantage of preparing the products optimally for insertion in the respective blisters, removing from the line the problems which might relate to special product shapes and/or arrangement of the blisters on the heat-formed ribbon, which can lead to insertion difficulties, thus limiting the risk of having defective blisters; a disadvantage, however, is that there is greater organ complexity, making them more expensive and the system excessively rigid, all of this resulting in long and laborious interventions for setting up the machine for a product format change and/or the blister pack change.
The described prior art solutions exhibit both advantageous and disadvantageous aspects which make one or the other preferable time by time, according to special needs. Each however lacks the sufficient operative flexibility required for best exploiting the machine when changing the production requirements, in particular when changing the format of the articles and the mutual disposition of the blisters in the blister strips.
The above-described solutions can be used both with step-activated machines and with continuous machines; the speed of the latter represents a further variable which can modify, in obviously different ways, the operative functionality of the solutions.